Download New natural sugar-based surfactants intended for stabilization

Original article
UDC: 615.262.015.11
doi:10.5633/amm.2015.0105
NEW NATURAL SUGAR-BASED SURFACTANTS INTENDED FOR
STABILIZATION OF COSMETIC/DERMOPHARMACEUTICAL
VEHICLES – SAFETY AND EFFICACY ASSESSMENT
Marija Tasić-Kostov1, Snežana Savić2
University of Niš, Faculty of Medicine, Department of Pharmacy, Niš, Serbia1
University of Belgrade, Faculty of Pharmacy, Department of Pharmaceutical Technology and Cosmetology,
Belgrade, Serbia2
Despite a large number of different vehicles available nowadays, conventional
emulsion systems remain one of the most commonly used for cosmetic and dermatological
preparations. Popularly labelled as skin- and environmentally-friendly, alkyl polyglucoside
(APG) sugar-based emulsifiers have attracted considerable interest with regard to their
dermatological properties, since irritation potential of commonly used emulsifiers could
affect the functionality and safety of dermopharmaceutics. The aim of this study was to
promote the emulsion based on C16/18 APG as a prospective vehicle for topical drugs and
cosmetic actives assessing the safety for use and skin hydration capacity. In accordance
with the requirements of newer legislation in vitro, acute skin irritation test was performed
using cytotoxicity assay on artificial skin. The results were compared with in vivo data
obtained by measuring the skin biophysical parameters, such as: stratum corneum
hydration (SCH), erythema index (EI), and transepidermal water loss (TEWL). Parameters
were measured prior to (baseline values) and upon cessation of a 24-h occlusive treatment
in 14 healthy human volunteers. In vivo moisturizing capacity of the emulsions was
assessed in 16 healthy volunteers in a long-term trial measuring of SCH.
This study showed, investigating the most frequently used APG, that emulsions
based on these emulsifiers could probably be promoted as safe cosmetic/
dermopharmaceutical vehicles. Prospective safety for human use with the correlation
between in vivo and in vitro findings was shown. In addition, the investigated vehicle per
se showed an excellent skin moisturizing capacity which is essential in maintaining healthy
skin, but also in improving dermatitis, which follows most pathological skin conditions. Acta
Medica Medianae 2014;54(1): 34-39.
Key words: emulsifiers, alkyl polyglucosides, dermatological preparations,
cosmetics, in vivo/in vitro skin safety and efficacy, biophysical skin parameters, skin
hydration potential
Contact: Marija Tasić-Kostov,
Blvd.81. dr Zoran Đinđić,
Faculty of Medicine,Niš, Serbia
[email protected]
Introduction
Creams are a common type of delivery
systems in cosmetic and dermatological preparations, although a large number of different
vehicles are available nowadays (1). Particularly,
emulsions stabilized by lamellar liquid crystals
(LLC) are intensively investigated as carriers for
various
dermopharmaceutics/dermocosmetics,
considering their extensive similarity to the
systems found in a living organism (e.g. stratum
34
corneum (SC) lipid matrix), significant solubilisation capacity for lipophilic and hydrophilic
substances and particularly the potential for
sustained skin hydration (2,3). A formulation of
emulsions presents a real challenge, since the
whole series of general demands must be fulfilled:
physicochemical stability, chemical inertness, efficacious delivery of the active, satisfactory
aesthetic characteristics (a pleasing appearance
which is retained during storage), optimal sensory
attributes, pleasant skin feeling during application,
the optimal skin hydration potential (4,5).
Alongside the listed quality standards and expectations of demandable consumers, those emulsions must, in the first place, have a satis-factory
safety profile.
If emulsion vehicles are used as drug
carriers, they are then considered to be medicinal
products, and they are covered by special docuwww.medfak.ni.ac.rs/amm
Acta Medica Medianae 2015, Vol.54(1)
New natural sugar-based surfactants intended for stabilization...
mentation and registration requirements (6).
Pharmaceutical emulsion-type topical products
must fulfil the demands for the satisfactory safety
profile. On the other hand, cosmetic emulsions
must meet the safety requirements of the
Regulation (EC) 1223/2009 on cosmetics.
Among all the pharmaceutical and cosmetic
excipients used for emulsions, emulsifiers are
most often recognized as potential skin irritants
(7,8). The first step and a key feature in the
irritation process is the interaction of the
surfactant with the stratum corneum (SC) lipids.
The interaction leads to the damage of the skin
barrier, it reflects in the increased transepidermal
water loss (TEWL) and is often followed by an
inflammatory response. The application of emulsions stabilized with anionic emulsifiers is accompanied by adverse skin reactions (9), so,
today, they are considered obsolete. Non-ionic
surfactants, particularly polyethylene glycol (PEG)based ones (e.g. etoxylated fatty alcohols and
fatty amphiphiles), represented for a long time the
emulsifiers of choice, as those with the least
potential for irritancy (10) and with the ability to
form lyotropic liquid crystals in the presence of
water as well. However, the PEG-emulsifiers’
potential to induce the barrier impairment and
sporadic erythema on exposed healthy skin was
indicated (9), which could be a limiting application
factor. Some commonly used emulsifiers also have
the ability to induce phospholipid emulsification
contributing to cellular damage, which can result
in cytolytic process and the release of proteins,
lysosomal and cytoplasmic enzymes and inflammatory mediators (11-13). PEG-free sugar-based
surfactants – Alkyl Polyglucosides (APGs) gain
increasing attention due to advantages with
regard to their biodegradability and health of
consumers (14).
This study investigated one of the most
frequently used APG mixed emulsifier – Sepineo
SETM68 INCI/ Cetearyl Glucoside & Cetearyl
alcohol (Seppic, France). There is insufficient data
about its performances and skin safety aspects
assessed by manufacturer. The aim of this study
was to formulate multicomponent emulsion based
on this emulsifier, and to assess its skin irritation
profile and skin moisturizing capacity. Safety
profile was evaluated in vitro using an alternative
method for acute skin irritation test (a cytotoxicity
assay) (15), and in vivo on healthy human
volunteers in a 24h-study under occlusion using the
measure-ments of the following parameters: SC
hydration (SCH), transepidermal water loss
(TEWL), and skin erythema index (EI) (9). In
addition, we checked the in vivo moisturizing efficacy of this emulsion sample in short-term (3
hours) study measuring SCH.
7% (w/w) was formulated and marked as M68.
The sample was adequately preserved using Euxyl
K®300 (Schülke&Mayr, Germany) preservative
blend. The humectant used was glycerol (BASF,
Germany) at 2% (w/w). For the purpose of the
preparation of the sample, emulsifier and 16%
(w/w) oil phase which consisted of: isopropylmiristate (Unichemcom, Austria), caprylic-capric
triglycerides (МyritolTM 318, Henkel, Germany),
decyl oleate (SabodermTM DO, SABO, Italy),
mineral oil (BASF, Germany), cetearyl alcohol
(Lanette 0, Cognis, Germany) and dimethicone
(Abil®100, Cognis, Germany) were heated at 70°C,
and then added to the preserved water phase at
the same temperature by stirring (stirrer RW16
basic, IKA®WERKE, Germany) at constant temperature for 5min (800rpm). Cooling was started
while mixing at 500rpm 3min, then at 300rpm to
the room temperature.
For the cell culture experiments, human
dermal fibroblasts from the foreskin of newborns
were used. These cells were obtained from Cascade
Biologics (Mansfield, UK), cultured according to
standard conditions and used from the third to the
twelfth passage. Immortalised keratinocytes from
the HaCaT-cell line (Human adult, low Calcium,
elevated Temperature) were used according to a
standard cell culture method during passages 68–
84 (16). For cytotoxicity (MTT) experiments, 3(4,5)-dimethylthiazol-2-yl)-2.5-diphenyl
tetrazolium bromide (Sigma, Steinheim, Germany),
sodium dodecylsulphate (Acros, B-Geel), isopropanol (RiedeldeHaën, Seelze, Germany), hydrochloric acid (Merck, Darmstadt, Germany) and
freshly double distilled water were used. Artificial
skin construct (ASC) was manu-factured and a
modified version of Mosman´s method (17) was
used for the in vitro acute skin irritation test-a
cytotoxicity assay as previously described (3).
Additionally, an in vivo bioengineering study
was also performed. Skin parameters TEWL, EI,
SCH were measured prior to (baseline values) and
60min upon cessation of 24h occlusive treat-ment.
Fourteen healthy female volunteers (27.4±1.1
years) were recruited. The flexor side of their left
forearms was treated with investigated emulsion
using precisely delineated and marked cardboard
ruler (with empty spaces in the form of rectangles,
16cm2 each). Two additional sites were left as a
non-treated control under occlusion (UCO) on the
right forearm and without occlusion (UC) on the
left. Sample was applied in quantity of 0.016g/cm2,
spread vigorously with rubber glove, and immediately covered with Parafilm® and than with
cotton adhesive tapes. All parameters were
measured according to the published guidelines
and documents (18).
To estimate the moisturizing efficacy of the
same sample in vivo by measuring EC, additional
group of 16 healthy volunteers (24.2±1.6 years)
was recruited. They all took part in short- (3h)
term trial. The flexor side of their left forearm was
treated with the emulsion sample using cardboard
ruler as described. One rectangle was left as an
Material and methods
A multiphase oil/water (o/w) cream based
on Sepineo SETM68 (kindly provided by Seppic,
France) sugar emulsifier in the concentration of
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New natural sugar-based surfactants intended for stabilization...
Marija Tasic-Kostov et al.
untreated control (UC) on the right forearm. The
amount of applied sample was 0.016g/cm2, and
the measurements conducted were: baseline, 1,2,
and 3 hours after application.
In vivo measurements were performed in
accordance with the Declaration of Helsinki, and
the volunteers signed a written consent. They
were informed of the study and instructed not to
use any skin cleansing or skin care product on the
test sites for the whole week before the study, and
during the experiment. The study was approved
by the local Ethical Committee on Human
Research. All subjects had healthy skin and no
known allergy to any ingredient of the sample.
Before any measurements were taken, the
subjects were asked to acclimatize for 30min
under controlled conditions (21±1°C and 50±5%
RH). TEWL was measured using Tewameter®TM
210, EI using Mexameter®MX 18, and SCH by
means of Corneometer®CM 825 (all Courage +
Khazaka, Germany).
All data were presented as means +/standard error of the means (SEM). In vivo
measured parameters (SCH, TEWL, EI) were
expressed as absolute changes to baseline (Δ
values) values, second versus first day for irritation
testing. The values obtained for M68 to UCO and
UC were compared using one-way ANOVA, followed
by Tukey’s t-test, where appropriate. For moisturizing efficacy testing SCH was presented as
percent change compared to baseline for M68 and
UC. SCH for the sample in distinct time points was
compared using a paired sample t-test.
The differences were accepted as statistically significant at p<0.05. Statistical analysis
was performed with commercial statistical software
SPSS for Windows 13.0.
sites and untreated controls, after 24h occlusion
related to the baseline values. All participants
reported strict compliance with the initially given
instructions.
Figure 1. In vitro skin irritation test, concentrationviability histograms for the sample M68
The results of the moisturizing efficacy of
the sample M68 are presented in Figure 3. The
application resulted in a significant improvement
of skin moisture (increase of SCH), compared to
both UC and baseline in a short-term study.
Results
The sample was applied to the ASCs in
three different concentrations: 0.25%, 2.5% and
25%. The results for the in vitro skin irritation test
are presented in Figure 1.
The results for in vivo investigation of skin
irritation potential are shown in Figures 2a, 2b.
Parameters were shown as ΔTEWL, ΔSCH and ΔEI
- absolute changes of mean values for treated
Figure 3. The effect of topical application of the sample
M68 related to baseline (percent change) in a shortterm study (SCH measurements). Significant
differences (P<0.05) are marked with (*)
a
b
Figure 2. In vivo skin irritation test - the influence of the sample M68 on parameters a) SCH, EI and b)TEWL and
both controls (under occlusion UCO and without occlusion UC); the results are shown as absolute changes of mean
values on the second vs. first day and standard error of means. Significant differences (P<0.05) are marked with
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Acta Medica Medianae 2015, Vol.54(1)
New natural sugar-based surfactants intended for stabilization...
(*) for denoting the differences between the baseline and obtained values, and also to mark the mutual
differences.
Discussion
Dermal irritation is defined as the production of "reversible damage of the skin following the
application of a test substance for up to 4 hours".
It was generally assessed by the potential of a
certain substance/product to cause erythema
/eschar and/or oedema after a single topical
application on rabbit skin and based on the Draize
score (19). In fact, skin irritation profile of topicals
and raw materials was, alongside other aspects of
toxicity, assessed routinely and reliably using in
vivo animal testing until recently. Ethical concerns
involving the use of laboratory animals, the validity
of animal skin as human skin models, and the need
for more efficient validation methods have
promoted the development of alternative methods
to assess irritation (15). Moreover, the sales ban
on animal-tested cosmetics prohibits the sale on
the EU market of any cosmetic product that has
been tested on animals or using alternative
methods other than those validated by the
European Centre for Validation of Alternative
methods (ECVAM) or the Organisation for European Economic Co-operation and Development
(OECD) (20). Nowadays, there are alterna-tive
ways to perform irritancy tests. The artificial skin
constructs are being used, employing alterna-tive
method for acute skin irritation test (cytotoxicity
assay) validated by ECVAM (21). In order to
compare the value of this in vitro test with the
actual outcome, parallel in vivo tests on humans
should normally be employed (22).
In accordance with the requirements of
current legislation, the determination of skin
irritation potential of APG based emulsion was
performed in our study using both described in
vivo and in vitro methods, which is compulsory in
order to draw a definitive conclusion on irritation
potential of the product. In this study, an in–house
three dimensional human skin model, involving
the reconstructed epidermis with functional stratum
corneum, was used for in vitro study. More
precisely, quantitative cell viability was determined as a percentage of negative control and is
used to predict the irritation potential – if the
mean cell viability is less than or equal to 50%, a
product can be defined as a local irritant; otherwise, its skin irritation profile could be characterized as favourable (19) which was shown for
our sample (Fig. 1).
Regarding in vivo measurements of the
skin, there is not a single biophysical parameter
efficient to embrace fully all pathophysiologic
aspects of skin irritancy. A multi-parametric approach in the assessment of the skin irritation
potential of topical emulsions is proposed when
employing biophysical measurements (14). The
effects of irritants have previously been studied by
measurements of transepidermal water loss (TEWL)
and skin color (23). Since the increase in TEWL is
observed after the application of skin irritants,
TEWL measurements are often used in support of
cosmetic claims of product mildness (18). Erythema
index (EI) measured by Mexameter® was shown to
be an adequate parameter for objective evaluation of skin irritation (24).
Investigated APG- based emulsion have
shown increased EI value after application, but no
statistically significant change was found (Fig. 2a).
This could support the claim that the investigated
emulsion is not expected to cause immediate
irritation of the skin. At the same time, the
emulsion efficiently hydrated the skin which is
shown as the SCH increase after 24h (Fig 2a).
Barrier function of the skin is dependent on
the intercellular lipid phase of SC; it has been
shown that changes in the lipid content and
organization of the intercellular lipids influence the
performance of the barrier (23). After the
application of the APG-based emulsion, the
decrease of TEWL was noticed (Fig. 2b), and it
could be interpreted as a repair of the barrier
function. This could probably be attributed to the
specific, skin-friendly colloidal structure of those
emulsion systems. It was shown that APG-based
vehicles mimic SC organization well, as the result
of lyotropic liquid crystals formation (3,15).
Similarity between the emulsions’ liquid crystalline
structure and the structure of physiological skin
lipids, rather than a simple deposition of lipid
material to the surface, is probably responsible for
the decrease in TEWL, that is, for a "strengthening" of the SC barrier. It is possible that this
beneficial effect is also the result of the increased
skin hydration, which consequently improves SC
elasticity.
In vivo/in vitro investigations in this study
showed the absence of skin irritation, pointing to
the satisfying skin safety profile of this emulsifier
and additional APG-based emulsions benefits to
the skin.
Topical moisturizers are essential in
enabling the skin to stay intact as well as in the
topical treatment of some diseases such are psoriasis, ichtyosis, atopic dermatitis (18). Thus, it
could be of great benefit for emulsion vehicle to
show good skin moisturizing potential and to
hydrate the skin even a few hours after its topical
application. Regarding our investigation, three
hours after the application of the sample M68,
significantly higher SCH compared to baseline was
measured, indicating significant potential of the
sample M68 for prolonged skin hydration (Fig. 3).
Conclusion
Overall, this study showed that C 16/18
APG-based vehicles could be promoted as safe for
cosmetic/dermopharmaceutical use. So far, there
has been a considerable body of evidence to
support the claim that APG emulsifiers, particularly
in the form of emulsifying waxes, could be used in
the formulation of advanced, sophisticated phar37
New natural sugar-based surfactants intended for stabilization...
Marija Tasic-Kostov et al.
maceutical and cosmetic emulsion-type topical
products. Comparison of the results from in vivo
skin irritation potential assessment for APG-based
emulsions with complementary in vitro cytotoxicity
assay from this study reveals a correlation
between the two confirming that topical emulsions
based on the most commonly used APG mixed
emulsifier are not expected to cause irritation of
the skin, when used in concentrations correspon-
ding to the therapeutic need, i.e. to the need of
the cosmetic treatment. Besides being mild to the
skin, the investigated agent plays an ameliorative
role in improving the overall health of the skin
barrier. Its use could be even taken into consideration when formulating emulsion vehicles for
cosmetic actives and drugs with unfavourable
safety profile.
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Acta Medica Medianae 2015, Vol.54(1)
New natural sugar-based surfactants intended for stabilization...
NOVIJI PRIRODNI ŠEĆERNI EMULGATORI NAMENJENI IZRADI
NOSAČA ZA DERMATOLOŠKE LEKOVE I KOZMETIČKI AKTIVNE
SUPSTANCE – ISPITIVANJE BEZBEDNOSTI I EFIKASNOSTI
Marija Tasić-Kostov1, Snežana Savić2
Univerzitet u Nišu, Medicinski fakultet, Farmaceutski odsek, Niš, Srbija1
Univerzitet u Beogradu, Farmaceutski fakultet, Katedra za farmaceutsku tehnologiju i kozmetologiju,
Beograd, Srbija2
Emulzije su najčešće korišćeni nosači u izradi kozmetičkih proizvoda i
dermatoloških lekova. Emulgatori, obavezni sastojci emulzija, mogu da poseduju visok
potencijal da iritiraju kožu i oštećuju njenu barijeru. Nasuprot konvencionalnim, alkil
poliglukozidi (APG) kao noviji, blagi, biodegradabilni emulgatori, danas privlače veliku
pažnju. Smatra se da, osim što ne iritiraju, pokazuju dodatne pozitivne efekte pri lokalnoj
aplikaciji kao što je vlaženje kože. Cilj studije bio je ispitivanje emulzija stabilisanih
jednim od najčešće korišćenih C16/18 APG, i to u smislu bezbednosti za upotrebu i
potencijala za hidrataciju kože. U skladu sa najnovijom zakonskom regulativom u ovoj
oblasti, potencijal za lokalnu iritaciju određen je in vitro testom citotoksičnosti na
veštačkoj koži, kao i in vivo merenjem biofizičkih parametara kože na humanim
dobrovoljcima: električna kapacitivnost (SCH), eritema indeks (EI) i transepidermalni
gubitak vode (TEWL). Merene su bazalne i vrednosti parametara 24h nakon aplikacije
uzorka okluzijom. Kapacitet uzorka da efikasno i produženo hidratiše kožu određivan je in
vivo merenjem parametra SCH nakon jednokratne aplikacije.
Ispitujući emulzije stabilisane jednim od najčešće korišćenih APG, studija je
pokazala da se ovi emulgatori verovatno mogu smatrati bezbednim u izradi kozmetičkih/dermofarmaceutskih nosača, pri čemu su rezultati in vivo i in vitro ispitivanja bili su u
međusobnom skladu. Nije registrovan iritacioni potencijal korišćenog APG, inače čest
problem pri upotrebi konvecionalnih emulgatora starijih generacija, a pokazan je odličan
potencijal emulzija sa C16/18 APG za efikasnu i prolongiranu hidrataciju. Poslednje može
biti od velikog značaja u tretmanu zdrave, ali naročito kože zahvaćene dermatitisom koji
je pratilac većine patoloških stanja kože. Acta Medica Medianae 2015;54(1):34-39.
Ključne reči: emulgatori, alkil poliglukozidi, dermatološki lekovi, kozmetički
proizvodi, in vivo/in vitro bezbednost i efikasnost na koži; biofizički parametri kože;
hidratacija kože
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